Release Behavior of 5-Fluorouracil from Chitosan-Gel Nanospheres Immobilizing 5-Fluorouracil Coated with Polysaccharides and their Cell Specific Cytotoxicity

Abstract

Small-sized chitosan-gel nanospheres, CNSs (average diameter 250 nm), containing 5-fluorouracil (5FU) or immobilizing 5FU derivatives (aminopentyl-carbamoyl-5FU or aminopentyl-ester-methylene-5FU) were prepared by the glutaraldehyde crosslinking technique and the emulsion method. When chitosan was crosslinked with glutaraldehyde, these 5FU derivatives were simultaneously immobilized to CNSs by means of Schiff's base formation. The CNSs were coated with anionic polysaccharides, such as 6-O-carboxymethyl-N-acetyl-α-l,4-polygalactosamine/Na (CM-NAPGA/Na), 6-O-carboxymethyl-chitin/Na (CM-chitin/Na), and sodium hyaluronate, through formation of a polyelectrolyte complex membrane to give CNS/polyanion, i.e., CNS/G, CNS/C, and CNS/H, respectively. The polyelectrolyte complex of polysaccharide was employed to achieve the controlled release and effective targeting of 5FU by the CNSs. The release rate of 5FU from the CNSs could be controlled by immobilization of 5FU, degree of deacetylation of chitosan used and coating with polysaccharides. Since very few galactosamine residues are known to be able to cross-react with ligands for galactose, the galactosamine residues on the surface of CNS/Gs are expected to act as the targeting moieties for hepatocyte. The CNS/G showed the lectinmediated aggregation phenomenon by the addition of APA lectin. Moreover, CNS/G had the highest cytotoxic activity among the three kinds of CNS/polyanion and CNS in HLE human hepatoma cell culture system in vitro.